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DPA membranes from Allochromatium vinosum cells, in which carotenoid biosynthesis was inhibited using diphenylamine (DPA) were obtained, into which rhodopin was incorporated. The LH2 complex with rhodopin content of 85% was isolated. Using a test for the thermal stability of LH2 complexes (DPA and with incorporated rhodopin), it was established that carotenoids of the early stages of biosynthesis (≤1 molecules per complex) did not interfere with rhodopin incorporation. It was found that when the LH2 complex with incorporated rhodopin was irradiated with light at the wavelength of 502 nm, BChl850 was photobleached at a rate close to that in the control LH2 complex. This indicates that rhodopin, after being incorporated into the DPA LH2 complex, is capable of generating singlet oxygen under illumination. Previously obtained data on heterogeneity of the carotenoid composition in DPA LH2 complexes (variation in the number of individual carotenoids molecules per complex in the general population) and our earlier suggestion about the structural role of carotenoids, namely, their ability to stabilize the LH2 complexes, were confirmed. Based on analysis of our results, as well as of the literature data, the interaction of singlet oxygen and carotenoids is discussed. [ABSTRACT FROM AUTHOR]

The effect of nanosecond repetitive pulsed microwave radiation (RPMR) (50–4000 pulses, pulse repetition rate of 13 Hz, peak power flux density (pPFD) of 140 W/cm2, and carrier frequency of 10 GHz) on the stimulation of proliferation of mesenchymal stem cells (MSCs) is investigated. The effect of exposure was assessed by the change in the number of cells in the culture after a single irradiation with different numbers of pulses. The effect was the most pronounced after exposure with 100 and 50 pulses; the maximum rate of the effect realization is in 24 h. [ABSTRACT FROM AUTHOR]

The effect of the qualitative and quantitative content of carotenoids on the assembly of light-harvesting complexes isolated from the heat-resistant purple sulfur bacterium Thermochromatium (T.) tepidum was studied. To decrease the content of carotenoids in the photosynthetic membranes and complexes, an inhibitor of carotenonegesis, diphenylamine (DPA), was used. The minimum carotenoid content of 40% was observed in T. tepidum cells grown in the presence of 120 μM DPA. At higher DPA concentrations, the growth of the culture stopped. Photosynthetic membranes and LH2 and LH1-RC complexes were isolated from DPA-treated cells; carotenoid content of these structures was 45 and 55%, respectively. Their spectral characteristics in the near IR region did not depend on the amount of carotenoids in the complexes and were similar to those of the native wild-type complexes. Simultaneously with a general decrease in the content of carotenoids, carotenoids from earlier stages of biosynthesis, such as neurosporene, ζ-carotene, and their hydroxy derivatives, appeared in the DPA-treated complexes. Emergence in DPA-treated complexes of carotenoids with a shorter chain of conjugated double bonds than in the control resulted in an increase in the efficiency of energy transfer from carotenoids to bacteriochlorophyll. [ABSTRACT FROM AUTHOR]

Regardless of cultivation conditions, two types of LH2 complexes are always assembled in photosynthetic membranes of Thiorhodospira (T.) sibirica: short-wave B800−830 and long-wave B800−850. The present work studied the effect of qualitative and quantitative content of carotenoids on assembling of these complexes. Diphenylamine (DPA), an inhibitor of carotenoid biosynthesis, was used to decrease the content of carotenoids in photosynthetic membranes and the complexes. In the cells of T. sibirica strain A12T, inhibition of carotenoid biosynthesis ranged from 40 to 50%. Complete suppression of carotenoid biosynthesis was achieved only once, which resulted in absorption spectrum changes of the DPA-LH2 complexes and lower stability of their structure; they were often destroyed during the isolation. The use of DPA with the cells of T. sibirica strain Kir-3 was more efficient. From inhibited cells of this strain, B800−850 and B800−830 complexes were isolated, in which the carotenoid content decreased to 80, 50, and 10%. Their spectral characteristics in the near infrared region were independent of the carotenoid quantity in the complexes and were similar to those of native complexes of the wild-type. At higher DPA concentration in the cultivation medium, accompanied by a decrease of the overall carotenoid content, such carotenoids of the earlier stages of biosynthesis as neurosporene, ζ-carotene, and their hydroxy derivatives, were found in the complexes. The efficiency of energy transfer from carotenoids to bacteriochlorophyll in all LH2 complexes was not shown to depend on the composition and quantity of carotenoids in the samples and was ~40%. Since the near-infrared spectrum of the LH2-complex of the B800−850 type was similar to that of the B800−850 complexes from Rhodospirillum molishianum, with 8 pairs of α/β-heterodimers forming the basis of their structure, it is possible to assume that the structure of the studied B800−850 complex from T. sibirica also consists of 8 pairs of α/β-heterodimers. A single carotenoid molecule is known to occur per the α/β-heterodimer; therefore, on average less than one carotenoid molecule (8 × 0.1 = 0.8) occurs per an LH2 complex from T.sibirica with 10% carotenoid content. This implies that the population of LH2 complexes contains both carotenoidless LH2 complexes and the complexes containing one or more carotenoid molecules. Obviously, LH2 complexes of both types are assembled regardless of the quantity of carotenoids per a complex, and carotenoids are not the required component for their correct assembly in vivo. [ABSTRACT FROM AUTHOR]

The results of assembling the light-harvesting complexes in the cells of the purple sulfur bacterium Thiorhodospira (T.) sibirica strain Kir-3 while suppressing the biosynthesis of carotenoids with diphenylamine (DPA) were studied. LH2 complexes (B800-850 and B800-830) with different carotenoid composition were isolated from the cells obtained. Maximum inhibition of carotenoid biosynthesis (~90% of the control) was reached at an inhibitor concentration of 53.25 μM (9 mg/L). It was established that changes in the qualitative and quantitative composition of carotenoids do not affect the assembly of B800-830 and B800-850 complexes. It is assumed that, in the population of DPA-LH2 complexes from T. sibirica strain Kir-3, both the carotenoidless complexes and the complexes containing one or two carotenoid molecules can be assembled. These results support the hypothesis that carotenoids are not required for assembling B800-850 and B800-830 complexes. [ABSTRACT FROM AUTHOR]

The experimental and calculated on the basis of density functional theory Raman spectra of plant and bacterial carotenoids (neurosporene, spheroidene, lycopene, spirilloxanthin, β-carotene, lutein, ζ-carotene, α-carotene, and γ-carotene) are analyzed. A number of characteristic features in the Raman spectra of carotenoids are described for the first time, which make it possible to determine the structure of the end groups of molecules and to distinguish their isomers. [ABSTRACT FROM AUTHOR]

Carotenoid mixture enriched by rhodopin and spirilloxanthin was incorporated in LH2 and LH1 complexes from Allochromatium ( Alc.) minutissimum in vitro. The maximum incorporating level was ~95%. Rhodopin (56.4%) and spirilloxanthin (13.8%) were incorporated into the LH1 complex, in contrast to the control complex, which contained primarily spirilloxanthin (66.8%). After incorporating, the LH2 complex contained rhodopin (66.7%) and didehydrorhodopin (14.6%), which was close to their content in the control (67.4 and 20.5%, respectively). Thus, it was shown that carotenoids from the total pool are not selectively incorporated into LH2 and LH1 complexes in vitro in the proportion corresponding to the carotenoid content in the complexes in vivo. [ABSTRACT FROM AUTHOR]

method of detecting the magnetic field variation is proposed and implemented experimentally. The method employs the rotation of the speckle pattern of light transmitted through an optical fiber that is placed into a longitudinal magnetic field and the recording of a holographic grating in a photorefractive crystal using the speckle field. The possibility of detecting the shape of a 0.15-s magnetic field pulse is demonstrated experimentally. [ABSTRACT FROM AUTHOR]

The effect of nanosecond repetitive pulsed microwave radiation (RPMR, 10 GHz, 100 ns pulse duration, 8 Hz pulse repetition rate, 140 and 1500 W/cm2 peak power flux density (pPFD)) on the regeneration of burn wounds in rats in dynamics was investigated. It is established that after 4-fold local irradiation of wounds with intensities of 140 and 1500 W/cm2 at frequency of 8 Hz, wound healing in the control and irradiated groups did not differ significantly (from the 1st day to the 14th day). Statistically significant acceleration of healing of irradiated burn wounds was detected from the 19th day. From the 12th day partial separation of the formed scab was observed. Epithelialization was observed from the 24th day to the 28th day. The effectiveness of RPMR with pPFD of 140 W/cm2 turned out to be higher in comparison with irradiation with pPFD of 1500 W/cm2. [ABSTRACT FROM AUTHOR]

Abstract: In order to determine the magnetic fluid stability, the method of investigation of magnetic particles redistribution processes according to change in time of magnetization in the nonuniform magnetic field in the device was used. The Hall-type microsensors with the sensitive element volume and the differential instrument for magnetic structure measurement were created and used in the device. The magnetic fluids sedimentation stability coefficients, with different initial magnetization, were determined. [Copyright &y& Elsevier]

The primary processes of photosynthesis for purple photosynthesising bacteria occur in light-harvesting (LH) complexes. The LH2 complex contains polypeptides; bacteriochlorophyll; and, in most cases, carotenoids. There are three known spatial structures of LH2 complexes from purple nonsulfur bacteria; however, high-resolution structures have not been established for purple sulfur bacteria. The results of the structural study of two light-harvesting complexes LH2 from purple sulfur bacteria Ectothiorhodospira haloalkaliphila by cryoelectronic microscopy are reported. Images of carotenoid-containing (LH2+) and carotenoidless (LH2–) variants of the complex, demonstrating a characteristic architecture of the objects of this type, are obtained. A 3D reconstruction of LH2+ is performed with a resolution of 4.5 Å; it coincides with the previously established crystal structure. The presence of particles of different morphology is shown for LH2–. [ABSTRACT FROM AUTHOR]

In this study we have demonstrated the possibility of phototrophic hydrogen production in C. reinhardtii under N-deprived conditions. When tested under air + CO 2 , and Ar + CO 2 N-deprived C. reinhardtii demonstrated decrease in PSII activity mainly due to over reduction of PQ, in addition no ascorbate accumulation was observed in cells. Under air + CO 2 atmosphere cells accumulated excessive amounts of starch. When incubated under Ar + CO 2 atmosphere cells accumulated starch as nitrogen replete cultures and no hydrogen production was observed. Hydrogen production (86 ml H 2 per one l of culture) occurred under Ar + CO 2 atmosphere when particular two-step illumination protocol was implicated. In oxygen producing and early oxygen consuming stage cells were illuminated under light intensity 169 μE m−2 s−1. When light was switched to 30 μE m−2 s−1, cultures quickly respired all oxygen and transient to anaerobic conditions with subsequent hydrogen production 2 h later. Actual quantum yield of C. reinhardtii cultures was measured in photobioreactor and maximal quantum efficiency of PSII of dark adapted cells together with JIP test were studied. • Photoautotrophic Chlamydomonas reinhardtii under N deprivation were studied. • Under air cultures accumulated starch and moderately decreased PSII activity. • Under Ar cultures decreased PSII activity and transit to anaerobiosis. • Under Ar two step illumination protocol was applied for sustainable H 2 production. • Under this illumination protocol 80 ml of H 2 per one l of culture was produced. [ABSTRACT FROM AUTHOR]

The possibility of singlet oxygen generation in five species of photosynthetic bacteria under irradiation with light was studied using the Singlet Oxygen Sensor Green (SOSG) dye that, when singlet oxygen is bound, is transformed into a fluorescent endoperoxide form. Irradiation was carried out using light of different spectral composition: red (absorption of bacteriochlorophyll, BChl) and white (absorption of BChl and carotenoids). No singlet oxygen generation was detected under red light irradiation, which indicated that BChl was not involved in this process. Under white light, as the irradiation time increased, an increase in SOSG fluorescence was recorded in the membranes of four bacterial species: Allochromatium vinosum MSU, Rhodobacter sphaeroides G1C, Rba. blasticus K-1 and Rhodopseudomonas faecalis. In Rba. sphaeroides, no increase in SOSG fluorescence was observed. It is assumed that in the white light this process occurs due to the pigments that absorb in the blue-green region of the spectrum, i.e. carotenoids with 8‒11 conjugated double bonds (neurosporene, spheroidene, lycopene, and rhodopin). Similar to Trolox, SOSG may slow down the bleaching process of BChl850 in the membranes of Alc. vinosum strain MSU and may therefore effectively perform the role of a singlet oxygen trap. [ABSTRACT FROM AUTHOR]

The effect of nanosecond repetitive pulsed microwaves (RPMs, 10 GHz, 100 ns pulse duration, 8 Hz pulse repetition rate, 140 W/cm2 peak power flux density (pPFD)) on the treatment of a model thermal burn of the skin of laboratory rats was investigated. It is established that after 4-fold local irradiation, the rate of wound healing increases; it is due to the accelerated formation of granulation tissue and a decrease in the thickness of the scab, which ensures scarless healing. [ABSTRACT FROM AUTHOR]

The direct action of singlet oxygen on the bacteriochlorophyll (BChl) of light-harvesting complexes in the membranes of four species of purple non-sulfur and sulfur photosynthesizing bacteria with and without carotenoids was studied. It was found that BChl in carotenoidless samples is generally more resistant to the action of singlet oxygen compared to the control. It is assumed that carotenoids are not required to protect BChl of bacterial light-harvesting complexes from singlet oxygen, and in the classic work by Griffith et al. [1] the apoptosis process in carotenoidless mutant cells, which involves the destruction of complexes, the appearance of monomeric BChl, and the generation of singlet oxygen caused by BChl, followed by BChl oxidation, was mistakenly attributed to the protective function of carotenoids. [ABSTRACT FROM AUTHOR]

The effect of singlet oxygen was studied in the system of Allochromatium (Alc.) vinosum MSU membranes, rose bengal, and light (547−600nm) with and without a quencher. In the system without a quencher, bleaching of the BChl850 band of the LH2 light-harvesting complex was observed and an absorption peak emerged at 698 nm, which belonged to the oxidized product, 3-acetyl-chlorophyll. The efficiency of five quenchers of singlet oxygen for neutralization of the effect of singlet oxygen on bacteriochlorophyll in the light-harvesting complexes of the membranes Alc. vinosum MSU was studied: sodium ascorbate, histidine, imidazole, trolox, and sodium azide. All of them, with the exception of sodium azide, neutralized successively the effect of singlet oxygen. [ABSTRACT FROM AUTHOR]

Seven different carotenoids with the number of conjugated double bonds (N) from 5 to 11 were incorporated in vitro into carotenoidless complexes LH2 of the sulfur bacterium Allochromatium vinosum strain MSU. The efficiency of their incorporation varied from 4 to 99%. The influence of N in the carotenoid molecules on the energy transfer efficiency from these pigments to bacteriochlorophyll (BChl) in the modified LH2 complexes was studied for the first time. The highest level of energy transfer was recorded for rhodopin (N = 11) and neurosporene (N = 7) (37 and 51%, respectively). In the other carotenoids, this parameter ranged from 11 to 33%. In the LH2 complexes studied, we found no direct correlation between the decrease in N in carotenoids and increase in the energy transfer efficiency from these pigments to BChl. [ABSTRACT FROM AUTHOR]

The possibility of embedding the carotenoids of spheroidene-branch biosynthesis (spheroidene and spheroidenone) from non-sulfur bacteria into the diphenylamine antenna complexes (DPA-complexes) from the sulfur bacteria Allochromatium minutissimum and Ectothiorhodospira haloalkaliphila with carotenoid synthesis inhibited by diphenylamine (DPA) was studied for the first time. It was found that spheroidene was embedded into the DPA-complexes from these bacteria at a level of 75-87%, with spheroidene embedding efficiency being 41-68% for the LH1-RC DPA-complexes and 71-89% for the LH2 DPA-complexes. The energy transfer efficiency from carotenoids to bacteriochlorophyll was shown to depend not only on the type of carotenoid but also on the very structure on the antenna complex. [ABSTRACT FROM AUTHOR]

Oxidation of bacteriochlorophyll (BChl) with potassium ferricyanide in membranes and LH2 complexes (carotenoid-less and control samples) from the purple bacteria Allochromatium minutissimum and Rhodobacter sphaeroides as well as BChl photobleaching in a model system have been studied. The oxidation of BChl depended on the type of bacteria. BChl850 was rapidly oxidized in samples from Alc. minutissimum, and BChl800 and BChl850 were slowly oxidized in samples from Rb. sphaeroides. The carotenoids were not involved in protecting BChl from chemical oxidation in the lightharvesting complexes. The appearance of BChl oxidation product was registered in the absorption spectra (absorption maximum about 700 nm) and by HPLC analysis. The oxidized BChl was identified as 3-acetyl-chlorophyll. It differed from BChl by the presence of a double bond in pyrrole ring II at the 7-8 position. The extinction coefficient of 3-acetyl-chlorophyll was about 10 times less than that of BChl850 in the LH2 complex from Alc. minutissimum. In the BChl → 3-acetylchlorophyll transition, the binding constant of the latter with LH2 complex as compared with that of BChl did not change dramatically, as indicated by: (i) preserved electrophoretic mobility of the complex; (ii) the presence of 3-acetyl-chlorophyll in the complex after separation; (iii) the presence of a 3-acetyl-chlorophyll CD signal that was proportional to its absorption spectrum. [ABSTRACT FROM AUTHOR]

The current generally accepted structure of light-harvesting LH2 complexes from purple phototrophic bacteria conflicts with the observation of singlet-triplet carotenoid excitation fission in these complexes. In LH2 complexes from the purple bacterium Allochromatium minutissimum, a drop in the efficiency of carotenoid triplet generation is demonstrated, which correlates with the extent of selective photooxidation of bacteriochlorophylls absorbing at ∼850 nm. We conclude that singlet-triplet fission of carotenoid excitation proceeds with participation of these excitonically coupled bacteriochlorophylls. In the framework of the proposed mechanism, the contradiction between LH2 structure and photophysical properties of carotenoids is eliminated. The possibility of singlet-triplet excitation fission involving a third mediator molecule was not considered earlier. [ABSTRACT FROM AUTHOR]